Pneumothorax and air travel

INTRODUCTION — It is estimated that over one billion passengers travel by air each year [1-3]. Although up to 5 percent of passengers have some form of disability or chronic medical illness, in-flight emergencies are infrequent [4]. Only one of every 39,000 passengers (0.003 percent) experiences an in-flight medical problem serious enough to come to the attention of emergency personnel [5,6]. Death during commercial flight is even rarer. During the year July 1998 to July 1999, the Federal Aviation Administration (FAA) collected medical events data, and 43 deaths occurred in-flight out of 600 million passengers [7].

The incidence, pathogenesis, and management of in-flight and previous pneumothorax/pneumomediastinum (PTX/PMD) will be reviewed here. Pre-flight medical assessment, the prevention of in-flight hypoxemia in patients with underlying lung disease, and the management of spontaneous PTX are discussed separately. (See "Assessment of adult patients for air travel" and "Evaluation of patients for supplemental oxygen during air travel" and "Treatment of secondary spontaneous pneumothorax in adults" and "Thoracostomy tubes and catheters: Indications and tube selection in adults and children" and "Treatment of primary spontaneous pneumothorax in adults" and "Pneumothorax: Definitive management and prevention of recurrence".)

INCIDENCE — The exact incidence of pneumothorax/pneumomediastinum (PTX/PMD) during commercial air travel is unknown due to non-standardized reporting requirements for in-flight medical emergencies, difficulty in making an in-flight diagnosis, and possible delay in symptoms [8]. Anecdotal reports of in-flight pneumothoraces have been published [9-11]. However, in-flight PTX must be rare, because it is not mentioned in most reports addressing in-flight emergencies [5,6,12-14].

A few reports have described the experience of individuals at high risk for pulmonary complications during air travel [15-17]:

●In a series of 1115 passengers referred to an airline medical advisory service for pre-flight evaluation, 704 had chronic obstructive pulmonary disease (COPD) or another pulmonary disorder [15]. Over 90 percent were "cleared" for transport. None of those cleared for air travel was known to have experienced a significant in-flight medical problem.

●Twenty of 21 patients flying from Israel to Europe and the United States for lung transplantation or thromboendarterectomy arrived safely [16]. However, one patient, who was hemodynamically unstable and requiring vasopressors and mechanical ventilation with a high concentration of oxygen (FiO₂ = 0.8), died of hypoxemia and shock after six hours of a relatively stable flight, presumably not due to a pneumothorax.

●Between 1986 and 1988, the Federal Aviation Administration (FAA) required air carriers to maintain records of all medical emergencies. A total of 2322 emergencies were documented during the two year period. Unfortunately, case descriptions were limited and the diagnoses were not necessarily confirmed medically. Only one definite and one possible PTX were reported [17].

In comparison, the reported incidence of spontaneous PTX not associated with air travel in the general population has ranged from 7 to 18/100,000 per year for males and 1 to 6/100,000 per year for females [18,19].

PMD during air travel has been described in a few case reports [20-22]. Precipitating factors have included upper respiratory tract infection, multiple Valsalva maneuvers in-flight and rupture of a bronchogenic cyst, although at least one PMD developed in-flight without an apparent precipitating event [21].

PATHOGENESIS — As altitude increases, both barometric (atmospheric) pressure and the atmospheric partial pressure of oxygen (PiO₂) both decrease. Thus, atmospheric pressure and PiO₂ are significantly lower at a typical aircraft cruising altitude of 40,000 feet than they are at sea level (table 1) [23]. At 40,000 feet (12,192 meters), the actual atmospheric pressure is 141 mmHg whereas pressurization of the cabin on commercial airliners maintains cabin atmospheric pressures around 565 mmHg (at sea level, atmospheric pressure is 760 mmHg) (table 1), which one would experience at an altitude of 8000 feet, called the "cabin altitude."

Regulatory government agencies, such as the Federal Aviation Administration (FAA), have requirements specifying that commercial aircraft cabins be pressurized to simulate a cabin altitude below 8000 feet (2438 meters) and allowing only brief diversions to a cabin altitude of 10,000 feet (3048 meters) for safety (eg, to avoid adverse weather). Different types of aircraft can achieve different degrees of pressurization, but most aircraft can be pressurized to 400 or 450 mmHg above the actual atmospheric pressure outside the aircraft (table 2) [23].

Boyle's law states that the volume of a gas is inversely proportional to the pressure to which it is exposed. Thus, as barometric pressure falls in the aircraft cabin during the ascent, trapped air in any non-communicating body cavity (eg, non-communicating pneumothorax [PTX], lung bleb, lung bulla, lung cyst, paranasal sinuses) will expand. Expansion of gas in the lungs is also increased by the high moisture content [24-26]. It is estimated that the volume of air in a non-communicating body cavity, such as a PTX, will increase by approximately 38 percent upon ascent from sea level to the maximum "cabin altitude" of 8000 feet (2438 meters) [27,28].

There are two main factors that might predispose certain individuals to PTX during air travel:

●Air trapping due to airway obstruction. Among patients who experienced a PTX in-flight, an increase in respiratory tract symptoms was noted in the days prior to air travel [9]. Perhaps mucous plugging of small airways caused increased air trapping, and expansion of the trapped air during the ascent to altitude ruptured the alveolar wall causing a PTX. The low PiO₂ at high altitude may further worsen airway obstruction and air trapping in patients with chronic obstructive pulmonary disease (COPD) by causing hypoxic bronchoconstriction [29].

●Expansion of air trapped in noncommunicating blebs, bullae, and intrapulmonary cysts. During ascent to altitude, the expansion of trapped air can lead to rupture and cause a PTX or pneumomediastinum (PMD) [25,30]. Further air expansion can convert a PTX to a tension PTX, resulting in life-threatening cardiopulmonary compromise [27,31,32]. Expansion of blebs at reduced ambient barometric pressure has been demonstrated radiographically [25]. Even without rupture, the expansion of trapped air in large non-communicating blebs, bullae, or cysts can potentially cause compression of functional lung, mediastinal shift, and circulatory compromise [7,10].

High performance aircraft pose a special problem due to the unique pulmonary effects of high gravitational forces (G-forces). Very low intrapleural pressures (-32 cm H₂O) over the apical surfaces of the lung have been noted at high G-forces [31]. PTX, mediastinal emphysema, and hemoptysis can result from these disruptive forces [31,33,34]. High G-forces do not occur during commercial air travel, but are important considerations for military aviators and test pilots who fly high performance aircraft.

CLINICAL MANIFESTATIONS — Pneumothorax (PTX) and pneumomediastinum (PMD) may present together or independently.

Symptoms of PTX arising at high altitude are the same as those at ground level. Chest pain (sometimes pleuritic) and dyspnea have been reported in confirmed cases [10,12-14]. When the PTX is large, characteristic physical findings include decreased chest excursion on the affected side, diminished breath sounds, and hyperresonant percussion. Subcutaneous emphysema may be present. Tension PTX is a life-threatening emergency that may complicate a spontaneous PTX. Clinical manifestations include tachypnea, tachycardia, hypoxemia, and hypotension. (See "Treatment of secondary spontaneous pneumothorax in adults" and "Clinical features, diagnostic approach, and treatment of adults with thoracic endometriosis".)

Symptoms and signs of a pneumomediastinum include chest pain (typically retrosternal), throat pain, dyspnea, and subcutaneous emphysema [35,36]. The key finding on physical examination is subcutaneous emphysema, usually over the neck and shoulders.

IN-FLIGHT MANAGEMENT OF PTX/PMD — For patients who develop symptoms and signs of a pneumothorax (PTX) or pneumomediastinum (PMD) while in-flight, administration of supplemental oxygen is the most important intervention. For patients with respiratory distress, emergency landing at the nearest airport will allow prompt evaluation and insertion of a chest tube, if needed. If there is not enough time to wait, a makeshift chest tube may be lifesaving by decompressing a tension pneumothorax, as has been described [37].

AIR TRAVEL WITH A PTX/PMD — Traditionally, the presence of a pneumothorax (PTX) at the time of a flight has been considered an absolute contraindication to air travel, and we still advise not travelling until complete resolution of a PTX has been documented [7]. However, the possibility that selected patients with a small, stable PTX may be able to travel safely for a short flight was examined in an observational study of 50 patients with a PTX following transthoracic needle aspiration biopsy [38]. Air travel within four days of a chest radiograph showing a residual PTX was not associated with any need for in-flight medical attention and less than 8 percent experienced minor chest symptoms during air travel. Further study is needed to evaluate the safety of short-duration air travel for patients with small, stable pneumothoraces, but without other underlying lung disease.

A separate report describes an uneventful flight of a patient with a PTX who had a chest tube in place with a unidirectional flutter valve (Heimlich valve) attached [39]. Emergent air travel of patients with pneumothoraces has been reported during war time [40]. Two of three such subjects who were transported at more than 9000 feet in an unpressurized cabin tolerated the trip; one died of bilateral pneumothoraces.

TIMING OF AIR TRAVEL AFTER PTX/PMD — The optimal length of time to wait after resolution of a pneumothorax/pneumomediastinum (PTX/PMD) before travelling by air is not known [41,42]. Data are mostly derived from retrospective studies that comprise heterogeneous populations. For patients with a prior PTX, the decision about air travel must be made on an individual basis, taking into consideration the likelihood of recurrence and how well the patient would tolerate a subsequent PTX. For example, a patient with relatively normal lung parenchyma could be permitted to fly two weeks after resolution of an iatrogenic PTX. However, air travel may be contraindicated in a patient with severe bullous emphysema, limited cardiopulmonary reserve, and a prior spontaneous PTX. The type of treatment the patient received (eg, simple aspiration, tube thoracostomy, chemical or mechanical pleurodesis) likely influences the risk of recurrence during air travel, although this has not been studied. (See "Treatment of secondary spontaneous pneumothorax in adults" and "Pneumothorax: Definitive management and prevention of recurrence".)

Experience is limited regarding the optimal timing. One study suggested that air travel should be avoided for at least two weeks following resolution of a traumatic PTX. In that study, among 12 patients with a recent traumatic PTX, those who waited for at least 14 days after radiographic resolution of the PTX were asymptomatic in-flight, while one of two patients who flew sooner than 14 days developed respiratory distress suggestive of a recurrent PTX [43]. In contrast, a retrospective series of patients with traumatic pneumothorax or hemothorax reported that, of the 58 patients who flew within nine days of chest tube removal, none had a complication [42]. In addition, 10 patients who flew with a small stable pneumothorax and five patients with an isolated pneumothorax on computed tomography had no complications during or following the flight.

Some experts recommend that stable patients with bullous emphysema who have had a previous PTX wait at least one year from the date of radiographic resolution of the PTX before considering air travel, although data supporting this advice are lacking [27,44].

TIMING OF AIR TRAVEL AFTER CARDIOTHORACIC SURGERY — The ideal time to delay air travel after cardiothoracic surgery is unknown. In a survey of 68 thoracic surgeons, 44 percent allowed their patients to fly after a variable length of time (up to 42 days) after complete radiographic resolution of a postoperative pneumothorax (PTX) [41]. Seventy-seven percent allowed their patients to fly without delay following mediastinoscopy, even with a residual pneumomediastinum (PMD) [41]. In this survey, the only adverse in-flight event reported was a case of thoracic pain during ascent of the air craft.

DISEASE-SPECIFIC MANAGEMENT — Bullous emphysema, idiopathic pulmonary fibrosis, lymphangioleiomyomatosis, and intraparenchymal lung cysts have been associated with an increased risk of pneumothorax (PTX) and pneumomediastinum (PMD). Limited data are available to guide recommendations for these patients regarding air travel, as described below.

Bullous emphysema — The large number of travellers with chronic obstructive pulmonary disease (COPD) combined with the low overall rate of PTX suggests that the absolute risk of in-flight PTX is low in these patients. However, patients with bullous emphysema likely have an increased risk of rupture of a bulla and development of a PTX during air travel, especially if they have had a previous PTX [27,44,45]. In addition, a PTX in such patients could lead to life-threatening cardiopulmonary compromise as a result of a low baseline arterial oxygen tension (PaO₂) and a lack of sufficient ventilatory reserve to hyperventilate in response to hypoxemia. Data are insufficient to calculate the exact risk of spontaneous secondary PTX for patients with bullous emphysema. (See "Treatment of secondary spontaneous pneumothorax in adults".)

Patients with COPD or bullous emphysema should be advised to postpone air travel should they develop an exacerbation of COPD. Chest imaging to exclude a PTX may be appropriate for patients who develop an increase in dyspnea just prior to air travel, because the presence of a PTX would be an absolute contraindication to air travel. A history of a prior spontaneous PTX in a patient with COPD likely increases the risk of in-flight PTX, because the risk of a second spontaneous PTX (without air travel) is approximately 50 percent over three years, unless the patient undergoes some form of pleurodesis. Some experts advise that patients with COPD delay air travel for one year after a spontaneous PTX. (See 'Timing of air travel after PTX/PMD' above and "Treatment of secondary spontaneous pneumothorax in adults".)

Patients with emphysema should be assessed for potential in-flight hypoxemia and supplemental oxygen supplied when necessary. (See "Evaluation of patients for supplemental oxygen during air travel", section on 'Screening for in-flight hypoxemia'.)

Interstitial lung disease — Idiopathic pulmonary fibrosis (IPF, also known as usual interstitial pneumonitis) and sarcoidosis are two of the more common types of interstitial lung disease. (See "Idiopathic interstitial pneumonias: Classification and pathology", section on 'Usual interstitial pneumonia' and "Clinical manifestations and diagnosis of sarcoidosis".)

At ground level, the risk of PTX and PMD are increased in patients with IPF. The natural history and clinical presentation of spontaneous PTX and PMD were examined in 72 patients with IPF who underwent chest computed tomography (CT) at a single institution [46]. Of the five patients with a PTX, four had acute dyspnea and pleuritic chest pain and one had no acute change in respiratory status. Of the four patients with a PMD, three had acute symptoms. Three of the PTX resolved by five months, while two loculated PTX were unchanged after five months [46]. Thus, PTX and PMD may be asymptomatic and may be chronic in patients with IPF. However, the added risk in patients with IPF who fly may not be great. As an example, one study that examined the risk of in-flight PTX by chest CT in 76 patients with IPF after 159 trips by air showed that no patient developed a PTX or PMD [47].

In sarcoidosis, granulomatous involvement of the lung interstitium and airways can lead to air trapping, pulmonary fibrosis, and lung cyst formation, all of which might theoretically increase the risk of altitude-related PTX and PMD. Among 92 patients with sarcoidosis who had chest CT scans after a total of 121 trips by air, none developed a PTX or PMD [47].

Thus, air travel appears reasonably safe for patients with interstitial lung disease. However, a preflight chest CT may be warranted in those with a history of a PTX or PMD within the previous six months or with an intercurrent exacerbation of respiratory symptoms.

Patients with moderate to advanced interstitial lung disease should be assessed for potential in-flight hypoxemia and supplemental oxygen supplied when necessary. (See "Evaluation of patients for supplemental oxygen during air travel", section on 'Screening for in-flight hypoxemia'.)

Lymphangioleiomyomatosis — Pulmonary lymphangioleiomyomatosis (LAM) is characterized by diffuse, cystic lung disease, presumably due to proliferation of atypical smooth muscle cells causing airway obstruction. Spontaneous PTX is a common complication of LAM. The risk of inflight pneumothorax and assessment of patients with LAM planning to travel by air are discussed separately. (See "Sporadic lymphangioleiomyomatosis: Treatment and prognosis", section on 'Air travel'.)

Intrapulmonary bronchogenic cyst — Intrapulmonary bronchogenic cysts have rarely been associated with PTX and PMD during ascent to high altitude by aircraft or train, sometimes in association with cerebral air embolism [22,24]. The incidence of PTX and PMD during air travel among patients with congenital intrapulmonary lung cysts is not known. However, among 15 patients with lung cysts complicating IPF who had a chest CT scan shortly after air travel, none had developed a PTX or PMD [47].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pneumothorax" and "Society guideline links: Management of inflight medical events".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Pneumothorax (collapsed lung) (The Basics)")

PATIENT PERSPECTIVE TOPIC — Patient perspectives are provided for selected disorders to help clinicians better understand the patient experience and patient concerns. These narratives may offer insights into patient values and preferences not included in other UpToDate topics. (See "Patient perspective: Lymphangioleiomyomatosis (LAM)".)

SUMMARY AND RECOMMENDATIONS

●Epidemiology – Development of a pneumothorax (PTX) or pneumomediastinum (PMD) during air travel is infrequent. However, patients with certain underlying lung diseases may be at increased risk for development of pneumothorax. Patients with poor respiratory reserve may not tolerate additional compromise to their lung function caused by a PTX. (See 'Incidence' above.)

●Pathogenesis – The pathogenesis of PTX and PMD follows Boyle’s law: the volume of a gas is inversely proportional to the pressure to which it is exposed. Thus, as an aircraft ascends during flight, barometric pressure falls, and trapped air expands in non-communicating body cavities (eg, pneumothoraces, lung blebs, lung bullae, lung cysts, paranasal sinuses). (See 'Pathogenesis' above.)

●Clinical features – The typical symptoms and signs of a PTX are chest pain (sometimes pleuritic) and dyspnea. Symptoms and signs of a PMD include chest pain (typically retrosternal), throat pain, dyspnea, and subcutaneous emphysema. (See 'Clinical manifestations' above.)

●In-flight management – For patients who develop symptoms and signs of a PTX or PMD while in-flight, administration of supplemental oxygen is the most important intervention. For patients with respiratory distress, emergency landing at the nearest airport will allow prompt evaluation and insertion of a chest tube, if needed. For tension pneumothorax in an unstable patient, in-flight chest decompression may be lifesaving. (See 'In-flight management of PTX/PMD' above.)

●Air travel with pneumothorax – A current PTX is a contraindication to commercial air travel. Patients who have a thoracostomy tube in place with a unidirectional valve (Heimlich valve) for decompression may be able to tolerate air travel when medically necessary. (See 'Air travel with a PTX/PMD' above.)

●Timing – For those patients with a history of a prior PTX, the decision about air travel must be made on an individual basis, taking into consideration the likelihood of recurrence and how well the patient would tolerate a subsequent PTX. For example, a patient with relatively normal lung parenchyma could be permitted to fly two weeks after resolution of an iatrogenic PTX. However, air travel may be contraindicated in a patient with severe bullous emphysema, limited cardiopulmonary reserve, and a prior spontaneous PTX. (See 'Timing of air travel after PTX/PMD' above.)

●Disease-specific management – For patients with radiographic resolution of a traumatic or spontaneous PTX, air travel is typically postponed for at least two weeks, although data are limited. For patients with underlying diseases that may predispose to recurrent PTX (eg, bullous emphysema, interstitial lung disease, lymphangioleiomyomatosis, intraparenchymal lung cysts, Birt-Hogg-Dubé), some experts suggest a longer delay or pleurodesis before air travel. (See 'Timing of air travel after PTX/PMD' above and 'Disease-specific management' above and "Birt-Hogg-Dubé syndrome" and "Treatment of secondary spontaneous pneumothorax in adults".)

•The ideal duration of time to delay air travel after cardiothoracic surgery is unknown. Most clinicians advise waiting three to four weeks after resolution of any postsurgical PTX. For patients who are stable after a mediastinoscopy, delaying air travel is usually not necessary in the absence of underlying lung disease. (See 'Timing of air travel after cardiothoracic surgery' above.)

•Bullous emphysema, interstitial lung disease, lymphangioleiomyomatosis, intraparenchymal lung cysts, and Birt-Hogg-Dubé have been associated with an increased risk of spontaneous PTX and PMD. Limited data are available to guide air travel recommendations for these patients. For those without a previous PTX, we typically obtain a pre-flight chest radiograph or computed tomography (CT) scan if the patient experiences an increase in dyspnea or onset of chest pain in the days to weeks prior to air travel. (See 'Disease-specific management' above.)

•Most experts advise patients to avoid air travel during an exacerbation of chronic obstructive pulmonary disease (COPD), due to a theoretic increase in risk of PTX from increased air trapping associated with an exacerbation. (See 'Bullous emphysema' above.)